Download targeting pharmacons to the brain via the nasal pathway

University of Szeged
Faculty of Pharmacy
TARGETING PHARMACONS TO THE BRAIN VIA
THE NASAL PATHWAY
Summary of Ph.D. thesis
Sándor Horvát
Supervisors:
Dr. Mária Deli, M.D., Ph.D.
Biological Research Center of The Hungarian
Academy of Sciences
Prof. István Erős, Ph.D., D.Sc.
Department of Pharmaceutical Technology
University of Szeged
Szeged
2009
1
1. INTRODUCTION
The blood-brain barrier (BBB) is a dynamic interface separating the brain from
systemic circulation. Therapeutical compounds to reach the central nervous system
need to pass through the brain capillaries, however they prevent the brain uptake of
98% of all potential neurotherapeutics. Due to specialised BBB functions only small
lipophilic molecules are able to penetrate freely into the brain tissue by passive
transport. In order to enhance the blood to brain transport and deliver drugs in
effective concentrations to the brain, several approaches have been attempted. These
methods include the modification of the drug molecules, or the manipulation of the
BBB. The selection of an application site circumventing the BBB is a third possibility.
Pharmacons can be dircetly targeted to the brain tissue, to the cerebrospinal fluid
compartments, or to tumor tissue by injections, medical sponges or minipumps. In
addition the nasal and ocular routes represent important new alternative gateways to
the brain. Intranasal delivery of drugs offers several advantageous properties. This
method is non-invasive, essentially painless, can be easily and readily administered by
the patient or a physician. Furthermore it ensures rapid absorption, the avoidance of
first-pass metabolism in gut and liver and does not require sterile preparations.
The unique anatomical and physiological properties of the olfactory region
provide both extracellular and intracellular pathways into the central nervous system
that bypass the BBB. The pathways employed for delivery of a particular drug from
the nose to the brain is highly dependent on various factors, such as the existence of
specific receptors on the olfactory neurons, the lipophilicity and the molecular weight
of the drug.
During the formulation of a dosage form intended for intranasal application
several aspects should be taken into consideration. Nasally administered drugs are
cleared rapidly from the nasal cavity into the gastrointestinal tract by the mucociliary
clearance system. The low membrane permeability and the junctional complexes of
nasal epithelial cells hinder the trans- and paracellular transport of large molecular
weight or polar drugs, and limit their nasal absorption. Moreover, the nasal mucosa
2
has a metabolic capacity as well, which can contribute to the low transport of peptides
and proteins across the nasal membrane. Because of these reasons application of
mucoadhesive agents to increase residence time of formulations on the nasal mucosa
and absorption enhancers to elevate drug transport across the nasal mucosa is crucial
in nasal vehicles.
Although a range of novel nasal products for systemic delivery of therapeutics
has reached the market already, there is still no drug exploiting the nasal route to treat
CNS diseases. Development of nasal delivery systems that enable rapid and efficient
concentration of drugs in the brain is a new and important field of investigation.
2. AIMS
Considering the above mentioned aspects of nasal drug targeting to the brain,
the importance of the permeability properties of the olfactory region, and the role of
nasal vehicles in drug delivery, the main aims of our experiments were the following:
(1) to reveal the protein composition of the junctional complexes of the olfactory
region by immunohistochemistry,
(2) to characterize the permeability of blood vessels in different parts of the
olfactory system,
(3) to formulate and characterize carrier systems for nasal delivery containing
bioadhesive and/or absorption enhancer components,
(4) to measure plasma and brain pharmacokinetics and bioavailability using
different nasal vehicles and as a test molecule fluorescein isothiocyanatelabeled dextran with an average molecular weight of 4.4 kDa (FD-4) in rats,
(5) to test the acute toxicity of nasal vehicles on the olfactory system.
3
3. MATERIALS AND METHODS
3.1. Antibodies and immunohistochemistry
To detect specific tight junction proteins in fixed olfactory and brain tissue,
polyclonal rabbit sera against claudin-1, claudin-3, claudin-5, claudin-19, occludin,
ZO-1, ZO-2, connexin-43, and monoclonal mouse antibody against ZO-1 were used as
primary antibodies. As secondary antibodies goat anti-mouse and anti-rabbit IgG
labelled with cyanin-derivative dye Cy3 or Cy2 were chosen. Nuclei were stained with
Sytox or Topro dyes.
3.2. Permeability studies
Vascular permeability of the olfactory system was demonstrated by
extravasation of the markers fluorescein (MW 376 Da) and Evan’s blue that binds
serum albumin (MW 67 kDa) injected intravenously to rats. When the permeability of
the blood vessels was tested by electron microscopy, 1% lanthanum nitrate was added
to the fixative used for transcardial perfusion.
3.3. Preparation of dosing solutions
Absorption enhancer Cremophor RH40 was dissolved in physiological saline
solution. Sodium hyaluronate was added in small amounts to the solution and to
ensure the complete solvation samples were rehomogenized after 24 h. The FD-4 was
dissolved in the prepared vehicles at a concentration of 1 mg/ml for intranasal and 8
mg/ml for intravenous administration.
Table 1. Compositions of the dosing solutions (in weight percentage)
Vehicle
Physiological saline
Sodium hyaluronate
Cremophor RH40
PhS
100.0%
-
-
AE
90.0%
-
10%
HA
98.5%
1.5%
-
MA
88.5%
1.5%
10%
4
3.4. Rheological measurements
Rheological measurements were carried out with a Rheostress 1 Haake
instrument. A cone-plate measuring device was used in which the cone angle was 1º,
and the thickness of the sample was 0.048 mm in the middle of the device. The flow
and viscosity curves of the samples were determined by changing the shear rate
between 0.01 and 100 s-1 at 37ºC.
3.5. In vitro drug release studies
Dissolution studies were carried out using ointment cells and small volume
dissolution vessels in a Hanson SR8-plus dissolution apparatus. Samples, 0.4 g each,
containing 1 mg/ml FD-4 were placed as donor phase on the Porafil membrane filter
(pore diameter 0.45 µm). PBS (pH = 7.4, 100 ml) was used as dissolution medium at a
temperature of 37ºC. Samples (3 ml each) were taken and immediately replaced with
fresh dissolution medium at 15, 30, 60, 120, 180, 240, 300, 360, 420 and 480 min, and
further analyzed by spectrofluorometry. Six parallel measurements were performed in
case of each dosing solution.
3.6. Animal experiments
Male Wistar rats (316 ± 48 g, 3-month-old) were used for all the studies.
3.6.1. Treatments
The rats were anesthetized ip. with tribromoethanol solution and they were
placed in supine position. An average of 40 µl solution was then administrated by
micropipette positioned 5 mm deep into the right naris to achieve the longest possible
residency time of the vehicle in the nasal cavity. In case of intravenous treatment 500
µl solution was injected into the tail vein of anesthetized animals. There were five
treatment groups, and five different time points, 30, 60, 120, 240 and 480 min, during
the experiments.
5
Table 2. The composition of the experimental groups.
Vehicle
Treatment
n
VFD-4
CFD-4
mFD-4
PhS
intravenous
4
500 μl
8 mg/ml
4000 μg
PhS
intranasal
4
40 μl
1 mg/ml
40 μg
AE
intranasal
4
40 μl
1 mg/ml
40 μg
HA
intranasal
4
40 μl
1 mg/ml
40 μg
MA
intranasal
4
40 μl
1 mg/ml
40 μg
n, number of animals/group; V, volume of the dosing solution given for treatment; C,
concentration of FD-4 in dosing solutions; m, quantity of FD-4 given in dosing
solutions/animal; PhS, physiological saline solution; AE, vehicle containing
absorption enhancer Cremophor RH40; HA, vehicle containing hyaluronan alone;
MA, vehicle containing mucoadhesive hyaluronan and absorption enhancer
Cremophor RH40.
3.6.2. Collection of plasma and brain samples for the measurement of FD-4 levels
In deep anesthesia blood was taken by cardiac puncture into heparinized tubes
from all four rats in each treatment group and at each time point, then the animals
were transcardially perfused. The brains were removed and 10 brain regions including
the olfactory bulb, frontal and parietal cortex from the left and the right side, the
hippocampus, the midbrain, the pons and the cerebellum were excised. The weight of
the brain samples was measured. Blood samples were centrifuged, and plasma and
brain samples were kept frozen until further investigations.
3.7. Determination of FD-4 concentration of samples
Brain samples were homogenized with 7.5% w/v trichloroacetic acid solution
in Potter–Elvehjem tissue grinder. Homogenized samples were centrifuged,
supernatants were neutralized. The FD-4 content of samples was determined by a PTI
spectrofluorometer (Photon Technology International Inc.) at excitation wavelength of
492.5 nm and emission wavelength of 514.5 nm. The sensitivity of the measurement
was 1 ng/ml FD-4 in the samples. Linearity of the measurement of FD-4 was r2 ≥
6
0.998, while the precision was found to be RSD ≤ 9.19 % across all the concentration
ranges used in the study.
3.8. Electron microscopy
Rats were transcardially perfused with 2.5% glutaraldehyde in 0.1 M
cacodylate buffer. The olfactory tissue was dissected out and postfixed in the identical
fixative for additional 4 h, and then stored in cacodylate until further processed.
Cerebral cortex, olfactory bulb, nasal mucosa were postfixed in 1% OsO4 in 0.1 M
cacodylate buffer and then dehydrated in an ethanol series. The specimens were
embedded, ultrathin sections were cut by ultramicrotome, mounted on pioloformcoated copper grids, contrasted with lead citrate and analyzed and documented with an
EM10A (Zeiss) electron microscope.
3.9. Statistical analysis
All data presented are means ± SEM or SD. The values were compared using
GraphPad Prism software. The analysis of variance was followed by Newman–Keuls
multiple comparison test. Changes were considered statistically significant at P < 0.05.
4. RESULTS AND DISCUSSION
4.1. Rheological measurements
Viscosity of the vehicle may influence the diffusion speed of the incorporated
drug, in this way play important role in the drug release process. Low shear stress
values and a linear correlation between shear stress and shear rate were measured for
both the physiological saline solution and the absorption enhancer containing system,
typical for Newtonian flow behavior. The addition of the surface active agent in AE
slightly increased the slope, reflecting the viscosity of the sample. The viscosity
values of HA and MA vehicles containing sodium hyaluronate were higher, than for
PhS and AE samples. HA and MA solutions can be characterized by pseudoplastic
flow behavior.
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4.2. In vitro drug release studies
Carriers PhS and AE, not containing biopolymer, showed similar dissolution
kinetics and profiles but in the case of vehicles containing the mucoadhesive
hyaluronan, HA and MA, different dissolution profile could be detected. The addition
of hyaluronan slowed the release of FD-4 between 30-240 min, but the same amount
of FD-4 was released from the vehicles at 8 hours.
4.3. The morphological basis of nasal pathway
4.3.1. Immunostainings of junctional proteins in the olfactory system
Epithelial and endothelial barriers separate the organisms from the external
environment and the body compartments from each other. The intercellular seals
responsible for the effective separation are called tight junctions (TJ). In our studies
we revealed by immunohistochemistry the junctional protein compositions of the
major barriers of the olfactory system. These are (i) the layers of epithelial cells
connected by apical TJ complexes, (ii) endothelial cells of the blood vessels in the
lamina propria and (iii) the olfactory ensheathing cells (OECs) and perineural cells
protecting the axons of the sensory olfactory neurons which are projected from the
periphery to the CNS.
Table 3. Summary of the immunohistochemical findings in the major barriers of the
olfactory system.
Junctional protein
Epithelial cells
Endothelial cells
OECs
ZO-1
+++
+++
+++
ZO-2
++
-
-
Occludin
+++
+
+++
Claudin-1
+++
-
-
Claudin-3
+++
-
-
Claudin-5
+++
+
++
Claudin-19
++
-
8
The TJ protein pattern of OECs is similar to that of endothelial cells, and may
consist of claudin-5, occludin and ZO1. According to our data the olfactory epithelial
layer presents the most complex and possibly the most tight barrier from the point of
view of drug targeting.
4.3.2. Permeability properties of the olfactory region
Dye study
We found that the blood vessels of the lamina propria in both the respiratory
and olfactory regions are highly permeable to the dyes fluorescein and Evan’s blue in
contrast to the vessels of the brain. These findings are in agreement with our data on
the protein composition of the endothelial TJs of the olfactory mucosa.
Lanthanum study
We demonstrated for the first time that the blood vessels of the lamina propria
of the olfactory mucosa are leaky for perfused lanthanum nitrate as an accepted
electron microscopical tracer. The OEC TJs form a barrier for lanthanum nitrate,
which is incomplete allowing a low amount of leakage from the interstitial to the
periaxonal space. This finding explains the morphological basis of the transport
pathway between the nasal cavity and the CNS via the olfactory nerve. Our data also
indicate, that if a molecule is transported across the olfactory epithelium with the help
of an appropriate nasal vehicle, the nasal pathway demonstrated for lanthanum can be
used to reach the CNS.
4.4. Nasal targeting of FD-4 test molecule by different vehicles in rat
The main finding of our studies is that the combination of the surfactant
Cremophor, as an absorption enhancer, and hyaluronic acid, as a viscosifying and
bioadhesive polymer, could significantly increase the nose to brain transport of the test
molecule FD-4, especially in the olfactory bulb and frontal cortex regions, 4 hours
after administration.
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Fig. 1. FD-4 concentrations in different brain regions measured 240 min after
different treatments
abc d
60
abc d
ng FD -4/m g brain
abc d
P hS iv.
40
P hS in.
AE in.
H A in.
abc d
M A in.
20
ad
ac d
abc d
abc d
0
OBR
OBL
FCR
FCL
PCR
PCL
HIP
MID
CER
PON
OBR: olfactory bulb from right side; OBL: olfactory bulb from the left side; FCR:
frontal cortex from the right side; FCL: frontal cortex from the left side; PCR:
parietal cortex from the right side; PCL: parietal cortex from the left side; HIP:
hippocampus; MID: midbrain; CER: cerebellum; PON: pons. Statistically significant
differences (P < 0.05) were detected in the MA group compared to the values
measured in aPhS iv. group; bPhS in. group; cAE group; dHA group. Data are
presented as mean ± SEM, n = 4.
We hypothesize that peptides or peptide fragments in the size range of 1-4 kDa
acting on neuropeptide or hormon receptors in the nervous system, eg. peptides
regulating appetite and body weight, could be targeted with the MA formulation for
therapeutical purposes.
4.4.1. Surfactants as absorption enhancers
The surfactant Cremophor RH40 was used as an absorption enhancer.
Although surfactants, which are non-specific permeation enhancers, can improve the
absorption of drugs by increasing their paracellular and transcellular transport via the
modification of the cell membrane, no increase in the brain FD-4 levels was observed
after application of AE vehicle compared to that of the PhS. A possible explanation
can be the fast removal of both vehicle from the nasal cavity by the mucociliar
10
activity. The higher test molecule levels in brain regions using MA formulation as
compared to HA clearly indicates that Cremophor played an important role in
enhancing the permeability for FD-4 of the main barrier of the olfactory system,
namely the epithelium.
4.4.2. Role of mucoadhesion in nasal vehicles
Although viscosity and mucoadhesion are key factors in nasal drug delivery,
and hyaluronates have excellent mucoadhesive properties, natural biocompatibility,
and lack of immunogenicity, only one study tested viscous sodium hyaluronate
solutions in nasal absorption so far, but pharmacokinetics in the blood or in the CNS
were not determined.
According to our data in contrast to the combination of hyaluronan with
Cremophor RH40 (MA vehicle) sodium hyaluronate alone (HA vehicle) did not
increase the amount of FD-4 transported to the brain in our experiments.
Table 4. Pharmacokinetic parameters in brain.
Vehicle
cmax [ng FD-4/mg brain]
tmax
AUC
Relative BA
mean  SD
[min]
mean  SD
mean  SD
PhS iv.
1.72  0.90
240
598  178
1.0  0.3
PhS in.
4.49  0.14
120
1523  97
254.7  16.3
AE in.
2.07  0.21
30
554  83
92.7  13.9
HA in.
1.39  0.09
60
431  52
72.2 ± 22.7
MA in.
15.21  9.11
240
3358  1713
561.5  286.5
AUC, area under the concentration-versus-time curve; BA, bioavailability compared
to the PhS iv. group; PhS, physiological saline solution; AE, vehicle containing
absorption enhancer Cremophor RH40; HA, vehicle containing hyaluronan alone;
MA, vehicle containing mucoadhesive hyaluronan and absorption enhancer
Cremophor RH40; n = 4.
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The difference between the efficacy of nasal vehicles HA and MA may
indicate, that optimal viscosity, supposed mucoadhesivity, longer residence time and
absorption enhancement induced by the nonionic surfactant all contributed to the
increased brain penetration of the test molecule.
The effect of MA is not related to elevation in plasma levels of FD-4, since
FD-4, injected intravenously, resulted in a high concentration in plasma, and a low
concentration in brain, due to the highly selective and strictly regulated transport
processes of the BBB. The nasal formulations led to negligible plasma concentration,
while the brain concentration of FD-4 in MA group exceeded that of the intravenously
administered FD-4. This clearly indicates the circumvention of the BBB and a direct
access to the CNS.
Table 3. Pharmacokinetic parameters in plasma.
Vehicle
cmax [ng FD-4/ml plasma]
tmax
AUC
Relative BA
mean  SD
[min]
mean  SD
mean  SD
PhS iv.
8253  848
30
592411  82638
1.00  0.14
PhS in.
6.52  3.16
30
1887  730
0.32  0.12
AE in.
3.04  2.35
30
1129  567
0.19  0.10
HA in.
4.36  0.53
30
1719  79
0.29  0.01
MA in.
9.73  6.27
120
1847  1060
0.31  0.18
AUC, area under the concentration-versus-time curve; BA, bioavailability compared
to the PhS iv. group; PhS, physiological saline solution; AE, vehicle containing
absorption enhancer Cremophor RH40; HA, vehicle containing hyaluronan alone;
MA, vehicle containing mucoadhesive hyaluronan and absorption enhancer
Cremophor RH40; n = 4.
Toxicity is a major issue in the development of formulations for the nasal
route. It is very important to note, that in our study the vehicle containing sodium
hyaluronate and Cremophor RH 40 did not induce tissue damage, epithelial or
subepithelial toxicity, or ciliotoxicity demonstrated by electron microscopy.
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5. SUMMARY
The delivery of hydrophilic drugs or large biopharmaceuticals to the nervous
system is still a big challenge. The blood-brain barrier prevents the brain penetration
of the great majority of possible therapeutical molecules. Targeting drugs to brain
tissue requires transport through the blood-brain barrier, or utilization of alternative
routes. Due to the specific anatomical and physiological properties of the olfactory
region, the nasal pathway can be exploited as a direct route to the nervous system.
The three major barriers of the olfactory system are the epithelial cells, the
endothelial cells of the blood vessels in the lamina propria and the olfactory
ensheating cells which protect the axons of the olfactory neurons. We revealed by
immunohistochemistry, that the tight junction protein pattern of rat endothelial and
olfactory ensheating cells are similar and consist of claudin-5, occludin and ZO-1. The
olfactory epithelial cells express also ZO-2, claudin-1, -3 and -19 in addition to the
proteins found in endothelial cells, indicating that they represent the most complex
and the tightest barrier from the point of view of drug targeting. In accordance with
these data we found that blood vessels of the lamina propria of the olfactory mucosa
are leaky for lanthanum, an electron microscopical tracer. The olfactory ensheating
cells also form an incomplete barrier for lanthanum allowing leakage from the
interstitial to the periaxonal space. This finding explains for the first time the
morphological basis of the transport pathway between the nasal cavity and the nervous
system via the olfactory nerve.
We designed and tested nasal vehicles to overcome these barriers and target the
test molecule fluorescein-labelled 4 kDa dextran by the nasal pathway to the brain in
rats. From the four tested vehicle, the combination of the surfactant Cremophor, as an
absorption enhancer, and hyaluronic acid, as a viscosifying and bioadhesive polymer,
could significantly increase the nose to brain transport of the test molecule, especially
in the olfactory bulb and frontal cortex regions. Morphological examination of the
olfactory system revealed no toxicity of the vehicles.
In conclusion, the nasal pathway has a potential for targeting therapeutical
drugs to the central nervous system by circumventing the blood-brain barrier.
13
6. ACKNOWLEDGEMENTS
I am grateful to my supervisor and my mentor, Dr. Mária Deli for her scientific
guidance, encouragement and support throughout my Ph.D. studies.
I would like to express my gratitude to my supervisor at the Department of
Pharmaceutical Technology Prof. István Erős.
I thank Dr. László Siklós, head of the Laboratory of Molecular Neurobiology
in the Institute of Biophysics, Biological Research Center, and Prof. Piroska Révész,
head of the the Department of Pharmaceutical Technology for their support.
We are indebted to Prof. Hartwig Wolburg for the scientific cooperation
between
the
research
groups
that
made
the
electronmicroscopical
and
immunhistochemical studies of the olfactory system possible.
I am grateful to Dr. András Fehér, Lóránd Kiss, Dr. Anita Kurunczi, Dr.
Levente Kürti, Dr. Péter Sipos, Andrea Tóth and Dr. Szilvia Veszelka for their
inspiring help in the studies.
I would like to thank Ngo Thi Khue Dung for the excellent technical
assistance.
I thank the members of the Group of Molecular Neurobiology their help and
friendship.
Finally, I am especially thankful to Izabella Jámbor and my family for their
love and untiring support during my studies.
The research was supported by grants from the Hungarian Research Fund
(OTKA T37834, M036252), the National Office for Research and Technology (RET
08/2004, GVOP-KMA-52) and the Foundation of Gedeon Richter.
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7. PUBLICATIONS, POSTERS AND CONFERENCE LECTURES
Publications related to the subject of the thesis
I. Wolburg H., Wolburg-Buchholz K.,·Sam K., Horvát S., Deli M.A., Mack A.F.
Epithelial and endothelial barriers in the olfactory region of the nasal cavity of the
rat.
Histochemistry and Cell Biology; 130: 127-140, 2008.
IF: 2.320 (2008)
II. Horvát S., Fehér A., Wolburg H., Sipos P., Veszelka S., Tóth A., Kis L., Kurunczi
A., Balogh G., Kürti L., Erős I., Szabó-Révész P., Deli M.A.
Sodium hyaluronate as a mucoadhesive component in nasal formulation enhances
delivery of molecules to brain tissue.
European Journal of Pharmaceutics and Biopharmaceutics; 72: 252-259, 2009.
IF: 3.344 (2008)
III. Horvát S., Kis L., Dr. Szabóné Dr. Révész P., Dr. Erős I., Dr. Deli M.
Hatóanyagok agyba juttatása a nazális útvonalon keresztül.
Gyógyszerészet; 53: 259-266, 2009.
IF: -
Posters and conference lectures related to the subject of the thesis
PP = Poster presentation, OP = Oral presentation
1. Deli M.A., Fehér A., Kurunczi A., Sipos-Bodó E., Veszelka S., Horvát S., Penke
B., Szabó-Révész P.,Targeting molecules to brain by intranasal delivery.
9th Symposium on Signal Transduction in the Blood-Brain Barriers, Salzburg,
Austria, September 7-10, 2006
OP
15
2. Kurunczi A., Fehér A., Veszelka S., Sipos E., Horvát S., Szabó-Révész P., Erős I.,
Párducz Á., Penke B., Deli M., β-amiloid peptid bejuttatás agyba intranazális úton
- egy új lehetséges Alzheimer-kór modell?
X. Alzheimer-kór konferencia, Szeged, Hungary, September 20-22, 2006
PP
3. Fehér A., Kurunczi A., Veszelka S., Sipos E., Horvát S., Párducz Á., Penke B.,
Deli M., Erős I., Révész P., Β-amiloid peptid központi idegrendszerbe irányuló
transzportjának vizsgálata intranazális alkalmazás esetén.
Gyógyszerkutatási Szimpózium, Debrecen, Hungary, November 24-25, 2006
OP
4. Horvát S., Fehér A., Kurunczi A., Veszelka S., Penke B., Erős I., Szabó-Révész P.,
Deli M., Molekulák agyba juttatása intranazális beadással.
Magyar Idegtudományi Társaság XI. konferenciája, Szeged, Hungary, January 2427, 2007
PP
5. Deli M. A., Horvát S., Fehér A., Veszelka S., Kurunczi A., Kürti L., Penke B.,
Erős I., Szabó-Révész P., Targeting molecules to brain by intranasal delivery.
Cerebrovascular Biology Conference, Ottawa, Canada, June 24-28, 2007
OP
6.. Fehér A, Horvát S., Veszelka S., Kurunczi A., Kürti L., Erős I., Deli M.A., Révész
P., Study of drug transport to the central nervous system following intranasal
administration.
BBBB Conference on Pharmaceutical Sciences, Tallinn-Tartu, Estonia, September
13-15, 2007
OP
7. Horvát S., Fehér A., Veszelka S., Kurunczi A., Kürti L., Penke B., Erős I., SzabóRévész P., Deli M.A., Bioadhesive formulations increase the brain targeting of
molecules by the nasal pathway.
16
Signal Transduction in the Blood-Brain Barriers, Potsdam, Germany, September
13-16, 2007
PP
8. Horvát S., Fehér A., Veszelka S., Kurunczi A., Kürti L., Penke B., Erős I., SzabóRévész P., Deli M.A., Bioadhesive formulations increase the brain targeting of
molecules by the nasal pathway.
7th Conference and Workshop on Biological Barriers and Nanomedicine,
Saarbrücken, Germany, February 20-29, 2008
PP
9. Horvát S., Fehér A., Veszelka S., Tóth A., Kis L., Sipos P., Kürti L., Erős I.,
Szabó-Révész P., Deli M.A., Sodium hyaluronate as a mucoadhesive component
in nasal formulation enhances delivery of molecules to brain tissue.
COST-ESF/IBRO
Training
School
“Neuroimaging
and
complementary
techniques” Belgrade, Serbia, June 29 - July 6, 2008
PP
10. Horvát S., Fehér A., Sipos P., Veszelka S., Tóth A., Kis L., Kurunczi A., Kürti L.,
Erős I., Szabó-Révész P., Deli M.A., A hialuronsav, mint mukoadhezív
komponens, növeli a molekulák agyba juttatását a nazális útvonalon keresztül.
A
Magyar
Gyógyszerésztudományi
Társaság
Ipari
Szervezete,
Gyógyszertechnológiai és Gyógyszerkutatási Szakosztályának Konferenciája,
Sopron, Hungary, September 25-27, 2008
PP
11. Horvát S., Deli M.A., Erős I., Gyógyszerbejuttatás az agyba a nazális út, mint
alternatív beviteli kapu felhasználásával.
Sófi József Alapítvány Konferencia, Szeged, Hungary, March 25, 2009
OP
17